*Institute for Environmental Studies, Charles University in Prague, Benátská 2, Prague 2, Czech Republic ** Institute of Chemical Process Fundamentals, Academy of Sciences of the Czech Republic, Rozvojova 135, Prague 6, Czech Republic J. Hovorka*, M.Braniš*, J.Schwarz** DIURNAL VARIATION OF SUBMICRON PM SIZE DISTRIBUTIONS AND GASEOUS POLLUTANT CONCENTRATIONS, PRAGUE 2004, POLLUTION SOURCE ESTIMATION

Motivation of our work three years of our air monitoring revealed frequent (30% of days) bimodal pattern of diurnal variation of NO x, NMHC, CH 4, CO partially SO 2 first mode 8-9 a.m.traffic rush hours second mode 8-10 p.m.NO rush hours ? ARE THESE MEASUREMENTS SITE SPECIFIC ? ? DOES AEROSOL BEHAVE SIMILARY? ? WHAT ARE LIKELY SOURCES?

Parameters determined 5 mins averages 14 – 710 nm aerosol size distribution (SMPS) 15 mins averages NO, NO 2, CO, SO 2, CH 4, Non-Methane HC, O 3 (Horiba 360) temperature, humidity, UV-A,B, wind speed/direction hourly averages PM 10 by  -attenuator, traffic volumes natural gas consumption in near-by stationary sources

Sampling site roof-top aerosol/gasses sampling in University botanical garden in the Prague city center at height about 25 m above the street no street canyon conditions duration –

University Botanic garden sampling site PRAGUE 2 Wind direction Hospital heating plant

University Botanic garden, roof-top sampling inlets

Roof-top sampling configuration

Diurnal variation of CO, NO, NO 2, SO 2, NMHC, CH 4 in Botanical garden in Prague center,

Calculated from data: Diurnal variation of PM 10 concentrations averaged over half a year 2004 at the CHMI sites in Prague center

Diurnal variation of PM 10 (Beta), PM 0.72 (SMPS) and total particle number ( nm) in Botanical garden, Prague center

? SPECIFIC SITE ? Recorded bimodal pattern is NOT site specific solely for our station but appeared at other sites situated near river valley Similar pattern in diurnal variation also recorded in other cities in Europe with similar urban architecture and local geography ? AEROSOL TEMPORAL CHANGES? Temporal variations of aerosol mass/number concentrations also exhibit similar pattern as gaseous components measured

? SOURCES ? nucleation: NO up to 10 of true nucleation events (banana shape) recorded within measured period long-range transport: NOparticle residence time too short, fast changes of number concentrations, bimodal pattern during low wind speed primary emissions from: traffic natural gas burning in major sources in proximity to the sampling site: Hospital heating plant Botanical garden boiler apartment/office boilers

Hourly averages of particle number size distribution , Prague. Number

Hourly averages of particle mass size distribution , Prague. Mass

Hourly averages of traffic volumes at the intersection near University Botanical garden during working days (yellow) and weekends (green)

Data source:

Diurnal variation of natural gas burnup in Hospital heating plant and Botanic garden boiler in Prague center on

Diurnal pattern of 20 min values (Sep-Dec 2004) of natural gas burnup by heating boiler in the Botanic garden

Estimated diurnal pattern of output of gas burning boilers in residential districts

FirstSecond ItemTime of day / hours Gaseous precursors5:30-9:0018:00-22:00 Aerosol Number6:30-11:0018:00-23:00 Aerosol Mass6:30-11:0018:00-23:00 Traffic volumes7:00-9:0015:00-18:30 Hospital heating plant4:00-7:00 Botanic garden boiler5:30-10:00 Residential boilers4:00-6:0018:00-22:00 Summary of peak values of gaseous precursors, aerosol concentrations and different sources outputs in Prague

CONCLUSIONS bimodal pattern of diurnal variation of aerosol concentration can be ascribed to traffic and natural gas burning as primary aerosol emission sources precise traffic and gas burning apportionment of total aerosol burden in urban atmosphere requires further data on gas burning boilers in residential areas

Acknowledgment Traffic counts performed by L.Betuš and V.Klapšťová. The station was built and maintained with help of M.Civiš. The study was done within the scheme of project “Comprehensive characterization of atmospheric aerosol in Prague” No. 205/03/1560 of the Czech Grant Agency.